If you got this error during Provisioning a masked vdb, It can be related to the password change of the masking engine please make sure to do the necessary update according to the document.
Error during job execution
DB_PROVISION job for "ST-DELPHIXTEST1/VCrm_DB0" failed due to an
error during execution: Delphix Masking Engine returned an invalid response
Make sure the Delphix Masking Engine instance is online and available.
"Please see the dmsuite log for more details".
Make sure the Delphix Masking Engine instance is online and available.alert.jobs.failed.object